Optical semiconductor apparatus

ABSTRACT

An optical semiconductor apparatus includes: an optical semiconductor device including a translucent support substrate; a buffer layer on the support substrate, a seal ring in a frame shape provided in an outer region on the buffer layer, an active layer provided on an inner region of the buffer layer, and an electrode provided on the active layer. The optical semiconductor apparatus further including: a package substrate on which the optical semiconductor device is mounted; and a sealing part that seals a space between the seal ring and the package substrate.

RELATED APPLICATION

Priority is claimed to Japanese Patent Application No. 2016-237607,filed on Dec. 7, 2016, the entire content of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to optical semiconductor apparatuses, and,more particularly, to an optical semiconductor apparatus including anoptical semiconductor device.

2. Description of the Related Art

Nowadays, semiconductor light emitting devices such as light emittingdiodes and laser diodes that emit blue light have been in practical use.Development of light emitting devices that output deep ultraviolet lighthaving a shorter wavelength has also been pursued. Deep ultravioletlight has high sterilization capability. Semiconductor light emittingdevices capable of outputting deep ultraviolet light have thereforeattracted attention as a mercury free sterilization light source inmedical and food processing fields.

A light emitting device is housed in a package to protect the devicefrom an external environment. For example, a light emitting device issealed by bonding a substrate on which the light emitting device ismounted and a lid body provided on the substrate. A lid body is built bysetting a translucent window member in an opening of a metal frame body.A metal seal ring is provided on the outer circumference of thesubstrate, and the lid body is fitted between the metal frame body andthe seal ring via a brazing filler metal.

An increase in the complexity of the sealing structure for protectingthe device properly from an external environment leads to an increase inthe number of components and the manufacturing cost. It is thereforedesired to provide reliable sealing with a smaller number of components.

SUMMARY

In this background, one illustrative purpose of the present invention isto provide a technology for increasing the reliability of an opticalsemiconductor apparatus.

An optical semiconductor apparatus according to an embodiment of thepresent invention includes: an optical semiconductor device including atranslucent support substrate; a buffer layer on the support substrate,a seal ring in a frame shape provided on an outer region of the bufferlayer, an active layer provided on an inner region of the buffer layer,and an electrode provided on the active layer; a package substrate onwhich the optical semiconductor device is mounted; and a sealing partthat seals a space between the seal ring and the package substrate.

According to the embodiment, the active layer provided in the innerregion is sealed by the seal ring and the sealing part provided in ashape of a frame in the outer region of the optical semiconductordevice. Accordingly, the active layer, which needs be protected, issealed without using a package substrate or a lid body for sealing theactive layer by encircling the entirety of the optical semiconductordevice. Accordingly, the number of components required for sealing isreduced and the manufacturing cost is lowered, while at the same timemaintaining the reliability of sealing.

The support substrate may be a a sapphire (Al₂O₃) substrate, an aluminumnitride (AlN) substrate, or an aluminum gallium nitride (AlGaN)substrate, the buffer layer may include at least one of an AlN layer andan AlGaN layer that is undoped, and the active layer may contain AlGaN.

The optical semiconductor device may further include: a first clad layerprovided between the buffer layer and the active layer and on the outerregion and on the inner region of the buffer layer; and a second cladlayer provided between the active layer and the electrode. The seal ringmay be a first electrode provided on the outer region of the first cladlayer. The electrode on the active layer may be a second electrodeprovided on the second clad layer.

The optical semiconductor device may further include a first clad layerprovided between the buffer layer and the active layer and on the innerregion of the buffer layer, a second clad layer provided between theactive layer and the electrode, and a first electrode provided on afirst region in the inner region of the first clad layer. The activelayer may be provided on a second region in the inner region of thefirst clad layer different from the first region, and the electrode onthe active layer may be a second electrode provided on the second cladlayer.

The optical semiconductor device may further include an insulating layerthat covers an exposed portion of the first clad layer.

The insulating layer may further cover a side surface of the seal ring.

The first clad layer may be an n-type AlGaN layer, and the second cladlayer may be a p-type AlGaN layer, and the first electrode may be ann-side electrode, and the second electrode may be a p-side electrode.

The seal ring may be a multilayer film in which titanium (Ti)/platinum(Pt)/gold (Au) or chromium (Cr)/Pt/Au are layered on the buffer layersuccessively.

The sealing part may contain gold-tin (AuSn).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings that are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalfigures, in which:

FIG. 1 is a cross-sectional view schematically showing an opticalsemiconductor apparatus according to an embodiment;

FIG. 2 is a top view schematically showing an optical semiconductordevice of FIG. 1;

FIG. 3 is a cross-sectional view schematically showing a step ofmanufacturing the optical semiconductor apparatus;

FIG. 4 is a cross-sectional view schematically showing a step ofmanufacturing the optical semiconductor apparatus;

FIG. 5 is a cross-sectional view schematically showing a step ofmanufacturing the optical semiconductor apparatus;

FIG. 6 is a cross-sectional view schematically showing a step ofmanufacturing the optical semiconductor apparatus;

FIG. 7 is a cross-sectional view schematically showing a step ofmanufacturing the optical semiconductor apparatus;

FIG. 8 is a cross-sectional view schematically showing an opticalsemiconductor apparatus according to a variation;

FIG. 9 is a top view schematically showing a configuration of an opticalsemiconductor device of FIG. 8;

FIG. 10 is a cross-sectional view schematically showing an opticalsemiconductor apparatus according to another variation; and

FIG. 11 is a cross-sectional view schematically showing an opticalsemiconductor apparatus according to further another variation.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

A detailed description will be given of embodiments of the presentinvention with reference to the drawings. Same numerals are used in thedescription to denote same elements and duplicate descriptions areomitted as appropriate. To facilitate the understanding, the relativedimensions of the constituting elements in the drawings do notnecessarily mirror the relative dimensions in the actual apparatus.

FIG. 1 is a cross-sectional view schematically showing an opticalsemiconductor apparatus 10 according to an embodiment, and FIG. 2 is atop view schematically showing an optical semiconductor device 12 ofFIG. 1. The optical semiconductor apparatus 10 includes an opticalsemiconductor device 12, a package substrate 14, a sealing part 16, anda bonding part 18.

The optical semiconductor device 12 is a light emitting diode (LED) chipconfigured to emit “deep ultraviolet light” having a central wavelengthλ of about 360 nm or lower. To output deep ultraviolet light having sucha wavelength, the optical semiconductor device 12 is made of an aluminumgallium nitride (AlGaN) based semiconductor material having a band gapof about 3.4 eV or larger. The embodiment particularly discusses a caseof emitting deep ultraviolet light having a central wavelength λ ofabout 240 nm-350 nm.

In this specification, the term “AlGaN-based semiconductor material”refers to a semiconductor material mainly containing aluminum nitride(AlN) and gallium nitride (GaN) and shall encompass a semiconductormaterial containing other materials such as indium nitride (InN).Therefore, “AlGaN-based semiconductor materials” as recited in thisspecification can be represented by a compositionIn_(1-x-y)Al_(x)Ga_(y)N (0≤x+y≤1, 0≤x≤1, 0≤y≤1). The AlGaN-basedsemiconductor material shall contain AlN, GaN, AlGaN, indium aluminumnitride (InAlN), indium gallium nitride (InGaN), or indium aluminumgallium nitride (InAlGaN).

Of “AlGaN-based semiconductor materials”, those materials that do notsubstantially contain AlN may be distinguished by referring to them as“GaN-based semiconductor materials”. “GaN-based semiconductor materials”mainly contain GaN or InGaN and encompass materials that additionallycontain a slight amount of AlN. Similarly, of “AlGaN-based semiconductormaterials”, those materials that do not substantially contain GaN may bedistinguished by referring to them as “AlN-based semiconductormaterials”. “AlN-based semiconductor materials” mainly contain AlN orInAlN and encompass materials that additionally contain a slight amountof GaN.

The optical semiconductor device 12 includes a support substrate 20, abuffer layer 22, a first clad layer 24, an active layer 26, a secondclad layer 28, a first electrode 32, a second electrode 34, and aninsulating layer 36.

The support substrate 20 is a substrate having translucency for the deepultraviolet light emitted by the optical semiconductor device 12 and is,for example, a sapphire (Al₂O₃) substrate. The support substrate 20includes a first principal surface 20 a and a second principal surface20 b opposite to the first principal surface 20 a. The first principalsurface 20 a is a principal surface that is a crystal growth surface forgrowing the buffer layer 22 and the layers above. The second principalsurface 20 b is a principal surface that is a light extraction surfacefor extracting the deep ultraviolet light emitted by the active layer 26outside. In one variation, the support substrate 20 may be an aluminumnitride (AlN) substrate or an aluminum gallium nitride (AlGaN)substrate.

The buffer layer 22 is formed on the first principal surface 20 a of thesupport substrate 20. The buffer layer 22 is a foundation layer(template layer) to form the first clad layer 24 and the layers above.For example, the buffer layer 22 is an undoped AlN layer and is,specifically, an AlN (HT-AlN; High Temperature AlN) layer gown at a hightemperature. The buffer layer 22 may include an undoped AlGaN layerformed on the AlN layer. In one variation, the buffer layer 22 may beformed only by an undoped AlGaN layer when the support substrate 20 isan AlN substrate or an AlGaN substrate. In other words, the buffer layer22 includes at least one of an undoped AlN layer and an AlGaN layer.

The first clad layer 24 is formed on the buffer layer 22. The first cladlayer 24 is an AlGaN-based semiconductor material layer of the firstconductivity type. For example, the first clad layer 24 is an AlGaNlayer doped with silicon (Si) as an n-type impurity. The compositionratio of the first clad layer 24 is selected to transmit the deepultraviolet light emitted by the active layer 26. For example, the firstclad layer 24 is formed such that the molar fraction of AlN is 40% orhigher, and, preferably, 50% or higher. The first clad layer 24 has athickness of about 100 nm-300 nm. For example, the first clad layer 24has a thickness of about 200 nm. The first clad layer 24 is formedslightly inward of the buffer layer 22 and is formed to avoid theoutermost region 64 shown in FIG. 2. Therefore, a portion of the topsurface 22 a of the buffer layer 22 is exposed in the outermost region64.

The active layer 26 is made of an AlGaN-based semiconductor material andhas a double heterojunction structure by being sandwiched by the firstclad layer 24 and the second clad layer 28. The active layer 26 may havea monolayer or multilayer quantum well structure. For example, theactive layer 26 may be formed by stack of a barrier layer made of anAlGaN-based semiconductor material of the first conductivity type (e.g.,n type) and a well layer made of an undoped AlGaN-based semiconductormaterial. To output deep ultraviolet light having a wavelength of 355 nmor shorter, the active layer 26 is formed to have a band gap of 3.4 eVor larger. For example, the AlN composition ratio of the active layer 26is selected so as to output deep ultraviolet light having a wavelengthof 310 nm or shorter.

The active layer 26 is formed on the first clad layer 24. The activelayer 26 is not formed on the entirety of the first clad layer 24 and isformed only on an inner region 62 on the first clad layer 24. In otherwords, the active layer 26 is not formed in an outer region 60 outwardof the inner region 62. It can therefore be said that the region inwhich the active layer 26 is the inner region 62, and the region inwhich the active layer 26 is not formed is the outer region 60.

The second clad layer 28 is formed on the active layer 26. The secondclad layer 28 is an AlGaN-based semiconductor material layer of a secondconductivity type different from that of the first clad layer 24. Forexample, the second clad layer 28 is an AlGaN layer doped with magnesium(Mg) as a p-type impurity. The second clad layer 28 has a thickness ofabout 300 nm-700 nm. For example, the second clad layer 28 has athickness of about 400 nm-600 nm.

An electron block layer (not shown) may be provided between the activelayer 26 and the second clad layer 28. The electron block layer is anAlGaN-based semiconductor material layer of the second conductivity type(e.g., p type). For example, the electron block layer is formed suchthat the molar fraction of AlN is 40% or higher, and, preferably, 50% orhigher. The electron block layer may be formed such that the molarfraction of AlN is 80% or higher or may be made of an AlN-basedsemiconductor material that does not substantially contain GaN. Theelectron block layer has a thickness of about 1 nm-10 nm. For example,the electron block layer has a thickness of about 2 nm-5 nm.

The first electrode 32 is formed in the outer region 60 on the firstclad layer 24. In one example, the first electrode 32 is an n-sideelectrode connected to the n-type first clad layer 24. The firstelectrode 32 is formed by a multilayer film in which titanium(Ti)/platinum (Pt)/gold (Au) or chromium (Cr)/Pt/Au are layered on thefirst clad layer 24 successively.

The first electrode 32 is formed in a shape of a frame that surroundsthe inner region 62 in which the active layer 26 and the second cladlayer 28 are formed (see FIG. 2). The first electrode 32 is a seal ringfor sealing the structure provided in the inner region 62. For highsealing performance, the width w of the first electrode 32 correspondingto the difference between the outer dimension and the inner dimension ispreferably 100 μm or larger, and, more preferably, 200 μm or larger.

The second electrode 34 is formed on the second clad layer 28.Therefore, the second electrode 34 is provided in the inner region 62.In one example, the second electrode 34 is a p-side electrode connectedto the p-type second clad layer 28. The second electrode 34 is formed bya nickel (Ni)/gold (Au) multilayer film built on the second clad layer28 successively.

The insulating layer 36 is a passivation layer that covers and protectsthe exposed portions of the first clad layer 24, the active layer 26,the second clad layer 28, the first electrode 32, and the secondelectrode 34. The insulating layer is made of, for example, siliconoxide (SiO₂), silicon nitride (SiN), or the like. The insulating layer36 covers the side surface and top surface of the first clad layer 24and the side surface of the first electrode 32 in the outer region 60.The insulating layer 36 covers the side surfaces of the active layer 26,the second clad layer 28, and the second electrode 34 in the innerregion 62. The insulating layer 36 may cover a portion of the topsurface of each of the first electrode 32 and the second electrode 34.

The package substrate 14 includes a base 40, a first upper electrode 42,a second upper electrode 44, a first lower electrode 46, and a secondlower electrode 48. The base 40 is a plate-shaped member having a topsurface 40 a and a bottom surface 40 b. The base 40 is a ceramicsubstrate that contains alumina (Al₂O₃), aluminum nitride (AlN), etc.and is, for example, a high temperature co-fired ceramic (HTCC)multilayer substrate.

The first upper electrode 42 and the second upper electrode 44 areprovided on the top surface 40 a of the base 40. The first upperelectrode 42 is an electrode part bonded to the first electrode 32 ofthe optical semiconductor device 12 and has a frame shape correspondingto the first electrode 32. The second upper electrode 44 is an electrodepart bonded to the second electrode 34 of the optical semiconductordevice 12 and is provided inward of the first upper electrode 42 in aframe shape. The first upper electrode 42 and the second upper electrode44 are formed by plating a base member containing tungsten (W),molybdenum (Mo), etc. with nickel (Ni), gold (Au), etc. and has, forexample, a stack structure of W/Ni/Au.

The first lower electrode 46 and the second lower electrode 48 areprovided on the bottom surface 40 b of the base 40. The first lowerelectrode 46 and the second lower electrode 48 are electrodes formounting the optical semiconductor apparatus 10 on an external substrateor the like. The first lower electrode 46 is electrically connected tothe first upper electrode 42 inside the base 40. The second lowerelectrode 48 is electrically connected to the second upper electrode 44inside the base 40. The first lower electrode 46 and the second lowerelectrode 48 will be the anode electrode or the cathode electrode of theoptical semiconductor apparatus 10.

The sealing part 16 bonds the first electrode 32, i.e., the seal ring,and the package substrate 14 to seal a space therebetween. The bondingpart 18 bonds the second electrode 34 and the package substrate 14. Thesealing part 16 and the bonding part 18 contain gold-tin (AuSn) and ismade of, for example, a gold-tin alloy containing 20-30 weight percentof tin (Sn).

FIG. 2 schematically shows the outer region 60 and the inner region 62.For ease of understanding, the insulating layer 36 is omitted in FIG. 2.The outer region 60 is a region outward of a broken line 61 in theillustration, and the inner region 62 is a region inward of the brokenline 61. In this embodiment, the broken line 61 marking a boundarybetween the outer region 60 and the inner region 62 has a rectangularshape corresponding to the rectangular outer shape of the opticalsemiconductor device 12. In variations, the broken line 61 marking aboundary between the outer region 60 and the inner region 62 may beshaped in a circle, a polygonal (e.g., a triangle or a hexagon)different from a rectangle, or a loop having an irregular shape.

A description will now be given of a method of manufacturing the opticalsemiconductor apparatus 10. FIGS. 3-7 are cross-sectional viewsschematically showing steps of manufacturing the optical semiconductorapparatus 10. First, as shown in FIG. 3, the buffer layer 22, the firstclad layer 24, the active layer 26, and the second clad layer 28 areformed on the first principal surface 20 a of the support substrate 20successively. The layers formed on and above the support substrate 20can be formed by a well-known epitaxial growth method such as themetalorganic vapor phase epitaxy (MOVPE) method and the molecular beamepitaxial (MBE) method.

Subsequently, as shown in FIG. 4, portions of the active layer 26 andthe second clad layer 28 are removed in the outer region 60 so as toexpose a top surface 24 a of the first clad layer 24. Further, a portionof the first clad layer 24 is removed in the outermost region 64 toexpose a top surface 22 a of the buffer layer 22. The first clad layer24, the active layer 26, and the second clad layer 28 may be removed byreactive ion etching or dry etching using plasma, etc.

Subsequently, as shown in FIG. 5, the first electrode 32 is formed onthe first clad layer 24 in the outer region 60, and the second electrode34 is formed on the second clad layer 28 in the inner region 62. Forexample, the first electrode 32 is formed as a multilayer film in whichTi/Pt/Au or Cr/Pt/Au are layered successively, and the second electrode34 is formed as a multilayer film in which Ni/Au are layeredsuccessively. The first electrode 32 and the second electrode 34 may beformed by electron beam deposition, sputtering, or the like.

Subsequently, as shown in FIG. 6, the insulating layer 36 is formed tocover the exposed portions of the first clad layer 24, the active layer26, and the second clad layer 28. The insulating layer 36 functions as apassivation layer for covering and protecting the exposed portions ofthe respective layers made of an AlGaN-based semiconductor material. Theinsulating layer 36 is formed to cover at least a side surface 24 b ofthe first clad layer 24 not sealed by the first electrode 32 and exposedoutside. The insulating layer 36 may be formed by plasma CVD, electronbeam deposition, sputtering, or the like.

As illustrated, the insulating layer 36 is formed to cover a sidesurface 32 b of the first electrode 32 and a side surface 34 b of thesecond electrode 34. By providing the insulating layer 36 on the sidesurfaces 32 b, 34 b of the first electrode 32 and the second electrode34, the first electrode 32 and the second electrode 34 are suitablyprotected. The insulating layer 36 may be provided on a portion of topsurfaces 32 a, 34 a of the first electrode 32 and the second electrode34. The insulating layer 36 is provided to respectively expose at leasta portion of the top surfaces 32 a, 34 a of the first electrode 32 andthe second electrode 34 so that the first electrode 32 and the secondelectrode 34 can be electrically connected to the package substrate 14.This completes the optical semiconductor device 12.

Subsequently, as shown in FIG. 7, a first bonding member 52 and a secondbonding member 54 are provided on the package substrate 14, and theoptical semiconductor device 12 is provided on the first bonding member52 and the second bonding member 54. The first bonding member 52 and thesecond bonding member 54 are preforms for bonding the opticalsemiconductor device 12 and the package substrate 14 and contain gold(Au) and tin (Sn). The first bonding member 52 and the second bondingmember 54 have a stack structure in which Au and Sn are alternatelylayered. The first bonding member 52 has a shape of a framecorresponding to the first electrode 32 and the first upper electrode42, and the second bonding member 54 has a shape of a framecorresponding to the second electrode 34 and the second upper electrode44. Each of the first bonding member 52 and the second bonding member 54may be temporarily fixed to the top surfaces 32 a, 34 a of the firstelectrode 32 and the second electrode 34 or temporarily fixed on thefirst upper electrode 42 and the second upper electrode 44. The firstbonding member 52 and the second bonding member 54 may be formed byelectron beam deposition or sputtering on the top surfaces 32 a, 34 a ofthe first electrode 32 and the second electrode 34 or on the first upperelectrode 42 and the second upper electrode 44.

A load 50 is applied while the first bonding member 52 and the secondbonding member 54 are being sandwiched between the optical semiconductordevice 12 and package substrate 14. The first bonding member 52 and thesecond bonding member 54 are heated and melted while the load 50 isbeing applied. The first bonding member 52 forms AuSn eutectic bondingbetween the Au layer of the first electrode 32 and the Au layer of thefirst upper electrode 42 to form the sealing part 16. The second bondingmember 54 forms AuSn eutectic bonding between the Au layer of the secondelectrode 34 and the Au layer of the second upper electrode 44 to formthe bonding part 18. This completes the optical semiconductor apparatus10 shown in FIG. 1.

By providing the above-described configuration, the embodiment allowsthe active layer 26, the second clad layer 28, and the second electrode34 to be sealed by the first electrode 32 that define a framesurrounding the inner region 62 in which the active layer 26 isprovided, the package substrate 14, and the sealing part 16. As aresult, the active layer 26 is sealed without using a package substrateor a lid body for sealing the entirety of the optical semiconductordevice 12, and the number of components for sealing is reduced.Furthermore, sealing of the active layer 26 is completed merely bymounting the optical semiconductor device 12 on the package substrate14. Thus, according to the embodiment, the number of components isreduced and the manufacturing cost is reduced, while also maintainingthe reliability of the optical semiconductor apparatus 10.

According to the embodiment, sealing is performed by using a gold-tinalloy having a relatively low (about 300° C.) melting temperature sothat the impact of heat on the semiconductor layer during the sealingprocess is reduced. Further, sealing is performed by AuSn eutecticbonding instead of an adhesive member of, for example, resin, whichcould be deteriorated when irradiated with deep ultraviolet light.Accordingly, the reliability of sealing is improved.

FIG. 8 is a cross-sectional view schematically showing an opticalsemiconductor apparatus 110 according to a variation. FIG. 9 is a topview schematically showing a configuration of an optical semiconductordevice 112 of FIG. 8. The variation differs from the embodimentdescribed above in that a seal ring 130 in a frame shape is providedside from a first electrode 132 and a second electrode 134 of an opticalsemiconductor device 112. The following description of the variationhighlights the difference from the embodiment described above.

The optical semiconductor apparatus 110 includes an opticalsemiconductor device 112, a package substrate 114, a sealing part 116, afirst bonding part 117, and a second bonding part 118. The opticalsemiconductor device 112 includes a support substrate 120, a bufferlayer 122, a first clad layer 124, an active layer 126, a second cladlayer 128, a seal ring 130, a first electrode 132, a second electrode134, and an insulating layer 136. The package substrate 114 includes abase 140, a sealing metal layer 142, a first upper electrode 143, asecond upper electrode 144, a first lower electrode 146, and a secondlower electrode 148.

The support substrate 120 includes a first principal surface 120 a thatis a crystal growth surface and a second principal surface 120 b that isa light extraction surface. The buffer layer 122 is provided on thefirst principal surface 120 a of the support substrate 120. The firstclad layer 124 is provided on an inner region 162 of the buffer layer122. The seal ring 130 in a frame shape is provided on an outer region160 of the buffer layer 122. The seal ring 130 is formed by a multilayerfilm in which Ti/Pt/Au or Cr/Pt/Au are layered on the buffer layer 122successively. The first electrode 132 is provided on a first region 166of the first clad layer 124. The active layer 126 is provided on asecond region 168 of the first clad layer 124 different from the firstregion 166. The second clad layer 128 is provided on the active layer126. The second electrode 134 is provided on the second clad layer 128.The insulating layer 136 covers the exposed portions of the first cladlayer 124, the active layer 126, and the second clad layer 128. Theinsulating layer 136 also covers the side surfaces of the seal ring 130,the first electrode 132, and the second electrode 134. The materialsforming the optical semiconductor device 112 are the same as those ofthe embodiment.

The sealing metal layer 142, the first upper electrode 143, and thesecond upper electrode 144 are provided on the top surface 140 a of thebase 140. The sealing metal layer 142 is a part bonded to the seal ring130 and has a frame shape corresponding to the seal ring 130. The firstupper electrode 143 is an electrode part bonded to the first electrode132 and is provided at a position corresponding to the first region 166.The second upper electrode 144 is an electrode part bonded to the secondelectrode 134 and is provided at a position corresponding to the secondregion 168. The sealing metal layer 142, the first upper electrode 143,and the second upper electrode 144 are formed by plating a base membercontaining tungsten (W), molybdenum (Mo), etc. with nickel (Ni), gold(Au), etc. and has, for example, a stack structure of W/Ni/Au. The firstlower electrode 146 and the second lower electrode 148 are provided onthe bottom surface 140 b of the base 140. The first lower electrode 146is electrically connected to the first upper electrode 143 inside thebase 140, and the second lower electrode 148 is electrically connectedto the second upper electrode 144 inside the base 140.

The sealing part 116 bonds the seal ring 130 and the sealing metal layer142 and seals a space therebetween. The first bonding part 117 bonds thefirst electrode 132 and the first upper electrode 143. The secondbonding part 118 bonds the second electrode 134 and the second upperelectrode 144. The sealing part 116, the first bonding part 117, and thesecond bonding part 118 contain gold-tin. For example, the parts aremade of a gold-tin alloy containing 20-30 weight % of tin (Sn).

FIG. 9 schematically shows the outer region 160 and the inner region162. The outer region 160 is a region outward of a broken line 161 inthe illustration, and the inner region 162 is a region inward of thebroken line 161. The seal ring 130 in a shape of a frame is provided inthe outer region 160. The inner region 162 is divided into a firstregion 166 and a second region 168. The first region 166 is a regionwhere the first electrode 132 is provided, and the second region 168 isa region where the second electrode 134 is provided. In the illustratedexample, each of the first region 166 and the second region 168 has arectangular shape, but the variation is non-limiting as to the shape ofthe first region 166 and the second region 168. For example, the secondregion 168 may be provided inside the first region 166. Conversely, thefirst region 166 may be provided inside the second region 168.

According to this variation, the seal ring 130 provided in the outerregion 160 seals the first clad layer 124, the active layer 126, thesecond clad layer 128, the first electrode 132, and the second electrode134 provided in the inner region 162. As a result, sealing is completedmerely by mounting the optical semiconductor device 112 on the packagesubstrate 114. Therefore, this variation, like the embodiment and theaforementioned variation, makes it possible to reduce the manufacturingcost of the optical semiconductor apparatus 110, while also reducing thenumber of components necessary to seal the active layer 126 andmaintaining the reliability.

FIG. 10 is a cross-sectional view schematically showing an opticalsemiconductor apparatus 210 according to another variation. The opticalsemiconductor apparatus 210 includes the optical semiconductor device12, the package substrate 14, the sealing part 16, the bonding part 18,and a resin protective layer 270. This variation differs from theembodiment described above in that the resin protective layer 270 isprovided around the optical semiconductor device 12. The followingdescription of the variation highlights the difference from theembodiment described above.

The resin protective layer 270 covers the exposed portion of the opticalsemiconductor device 12 mounted on the package substrate 14 to protectthe optical semiconductor device 12. The resin protective layer 270 ismade of a resin material having translucency. It is also preferred thatthe resin protective layer 270 be made of a material having a refractiveindex lower than that of the support substrate 20 that is the lightextraction surface. For example, fluororesin, silicone resin, epoxyresin, or the like may be used in the resin protective layer 270. Theresin protective layer 270 may function as a lens by being configured tohave a dome shape as illustrated.

According to this variation, the optical semiconductor device 12 isphysically protected by providing the resin protective layer 270. Theactive layer 26 of the optical semiconductor device 12 is sealed by theseal ring. It is therefore not necessary for the resin protective layer270 to have a high sealing performance. For example, a resin materialthat could be deteriorated by the deep ultraviolet light emitted by theoptical semiconductor device 12 may be used. In other words, it is notnecessary to select a resin material of the resin protective layer 270having a high durability against light and a high sealing performance,and a relatively inexpensive resin material can be used. Thus, accordingto this variation, the manufacturing cost is prevented from increasingsignificantly even when the resin protective layer 270 is provided.

FIG. 11 is a cross-sectional view schematically showing an opticalsemiconductor apparatus 310 according to further another variation. Theoptical semiconductor apparatus 310 includes the optical semiconductordevice 12, a package substrate 314, the sealing part 16, the bondingpart 18, a lid body 370, and an adhesive layer 372. This variationdiffers from the embodiment described above in that the opticalsemiconductor device 12 is housed inside a package base 340 having arecess 341, and a lid body 370 is provided to cover a space over therecess 341. The following description of the variation highlights thedifference from the embodiment described above.

The package substrate 314 includes a package base 340, a first upperelectrode 342, a second upper electrode 344, a first lower electrode346, and a second lower electrode 348. The package base 340 is providedwith a recess 341 that opens on a top surface 340 a and is shaped suchthat the circumference of the recess 341 is bounded in a frame shape.The first upper electrode 342 and the second upper electrode 344 areprovided on a bottom surface 340 c of the recess 341. The first upperelectrode 342 is bonded to the first electrode 32 by the sealing part16, and the second upper electrode 344 is bonded to the second electrode34 by the bonding part 18. The first lower electrode 346 and the secondlower electrode 348 are provided on a bottom surface 340 b of thepackage base 340. The lid body 370 is mounted on the top surface 340 aof the package base 340 via the adhesive layer 372.

The lid body 370 is a plate-shaped window member that transmits the deepultraviolet light emitted by the optical semiconductor device 12 and ismade of quartz (SiO₂), sapphire (Al₂O₃), or the like. The lid body 370is mounted on the top surface 340 a of the package base 340 by theadhesive layer 372. The adhesive layer 372 adhesively bonds the packagebase 340 and the lid body 370. The variation is non-limiting as to thematerial of the adhesive layer 372. For example, epoxy resin, acrylicresin, silicone resin, urethane resin, polyimide resin, polyamide resin,polyester resin, melamine resin, phenol resin, fluororesin, etc. may beused.

According to this variation, the optical semiconductor device 12 isphysically protected by housing the optical semiconductor device 12 inthe recess 341 of the package base 340 and covering the assembly by thelid body 370. The active layer 26 of the optical semiconductor device 12is sealed by the seal ring. It is therefore not necessary for theadhesive layer 372 to have a high sealing performance. For example, aresin material that could be deteriorated by the deep ultraviolet lightemitted by the optical semiconductor device 12 may be used. In otherwords, it is not necessary to select a material of the adhesive layer372 having a high durability against light and a high sealingperformance, and a relatively inexpensive resin material can be used.Thus, according to this variation, the manufacturing cost is preventedfrom increasing significantly even when the package base 340 and the lidbody 370 are provided.

Described above is an explanation based on an exemplary embodiment. Theembodiment is intended to be illustrative only and it will be understoodby those skilled in the art that various design changes are possible andvarious modifications are possible and that such modifications are alsowithin the scope of the present invention.

The embodiment and the variations described above have shown the opticalsemiconductor apparatus provided with a light emitting device. In afurther variation, the sealing structure described above may be used toseal a light receiving device. For example, the structure describedabove may be used to seal a light receiving device for receiving deepultraviolet light.

The embodiment and the variations described above have shown the case inwhich the first clad layer 24 is made of an n-type semiconductormaterial, and the second clad layer 28 is made of a p-type semiconductormaterial. In a further variation, the conductivity type may be reversed.The first clad layer 24 may be a p type, and the second clad layer 28may be an n type.

The embodiment and the variation described above have shown the case ofusing a high temperature co-fired ceramic (HTCC) multilayer substrate asa material of the substrate. In a further variation, the ceramicmaterial used may be a low temperature co-fired ceramic (LTCC)multilayer substrate containing silica (SiO₂), calcium oxide (CaO),boron oxide (B₂O₃), etc. In this case, the electrode or the sealingmetal layer may be formed on the substrate by using a metal materialhaving a relatively low melting point such as copper (Cu) and silver(Ag) in place of a high melting point material such as tungsten andmolybdenum and forming a multilayer film of Ni/Au on the base member.

What is claimed is:
 1. An optical semiconductor apparatus comprising: anoptical semiconductor device including a translucent support substrate;a buffer layer on the support substrate, a seal ring that is a metallayer in a frame shape provided on an outer region of the buffer layer,an active layer provided on an inner region of the buffer layer, and anelectrode provided on the active layer; a package substrate on which theoptical semiconductor device is mounted; and a sealing part that seals aspace between the seal ring and the package substrate.
 2. The opticalsemiconductor apparatus according to claim 1, wherein the supportsubstrate is a sapphire (Al₂O₃) substrate, an aluminum nitride (AlN)substrate, or an aluminum gallium nitride (AlGaN) substrate, the bufferlayer includes at least one of an AlN layer and an AlGaN layer that isundoped, and the active layer contains AlGaN.
 3. The opticalsemiconductor apparatus according to claim 1, wherein the opticalsemiconductor device further includes: a first clad layer providedbetween the buffer layer and the active layer and on the outer regionand on the inner region of the buffer layer; and a second clad layerprovided between the active layer and the electrode, the seal ring is afirst electrode provided on the outer region of the first clad layer,and the electrode on the active layer is a second electrode provided onthe second clad layer.
 4. The optical semiconductor apparatus accordingto claim 3, wherein an area of contact between the first electrode andthe first clad layer is larger than an area of contact between the firstelectrode and the sealing part.
 5. The optical semiconductor apparatusaccording to claim 3, wherein the optical semiconductor device furtherincludes an insulating layer that covers an exposed portion of the firstclad layer and a side surface of the first electrode.
 6. The opticalsemiconductor apparatus according to claim 1, wherein the opticalsemiconductor device further includes a first clad layer providedbetween the buffer layer and the active layer and on the inner region ofthe buffer layer, a second clad layer provided between the active layerand the electrode, and a first electrode provided on a first region inthe inner region of the first clad layer, the active layer is providedon a second region in the inner region of the first clad layer differentfrom the first region, the electrode on the active layer is a secondelectrode provided on the second clad layer, and the opticalsemiconductor device further includes an insulating layer that covers anexposed portion of the first clad layer, a side surface of each of thefirst electrode, the second electrode, and the seal ring, and a portionof a top surface of each of the first electrode, the second electrode,and the seal ring that faces the package substrate.
 7. The opticalsemiconductor apparatus according to claim 3, wherein the first cladlayer is an n-type AlGaN layer, and the second clad layer is a p-typeAlGaN layer, and the first electrode is an n-side electrode, and thesecond electrode is a p-side electrode.
 8. The optical semiconductorapparatus according to claim 1, wherein the seal ring is a multilayerfilm in which titanium (Ti)/platinum (Pt)/gold (Au) or chromium(Cr)/Pt/Au are layered on the buffer layer successively.
 9. The opticalsemiconductor apparatus according to claim 1, wherein the sealing partcontains gold-tin (AuSn).